There are various kinds of chairs and various improvements are carried out in accordance with the respective kinds. As an example, Patent Reference 1 discloses a chair in which a seat is inclined forward when a seated person leans on a backrest. On the other hand, Patent Reference 2 describes a chair in which when a person is seated, a seat is inclined centering on substantially a middle portion in a front and rear direction in a side view thereof and a backrest is inclined by being moved cooperatively with inclining the seat rearward. In both of the patent references, as means for cooperatively moving the backrest with the seat, a kind of a link mechanism is adopted.
According to Patent Reference 1, both of the seat and the backrest remain unchanged in attitudes thereof by only when a person is seated thereon, when the seated person leans on the backrest to apply a large moment to the backrest, a rear portion of the seat is pushed up upwardly to incline the seat forward by a principle of lever and it is an object of the invention to eliminate a sense of oppression of the thigh of a person in a rocking state.
On the other hand, according to Patent Reference 2, when a person is seated on the chair deeply, the attitude of the backrest remains unchanged so far as the person does not lean on the backrest, for example, when the person is seated on a front portion of the seat, the backrest is inclined forward considerably, and the back of the person is pushed by an upper portion of the backrest. Then, a user is brought into a state of falling forward to feel an unpleasant feeling, hence, a seated position is shifted rearward. According to Patent Reference 2, the person adopts a correct seating attitude by giving the pleasant feeling when the person is seated on the front portion of the seat. Therefore, the chair disclosed in Patent Reference 2 can be said to be a kind of a disciplinary chair.
Patent Reference 1: JP-B-44-20784
Patent Reference 2: JP-B-46-27517